Water-repellent additives have been incorporated into hydraulic cement-based products for decades, serving to resist moisture, such as rain water, from penetrating excessively into materials, such as masonry mortars. Reducing moisture penetration can help to resist mold and mildew, to protect against cracks, and to resist efflorescence stains. Reducing water absorption also prevents or minimizes the damaging effects of freeze-thaw cycles.
Although these water-repellent additives to cementitious materials have been relatively effective, their chemical composition is very similar to the chemical composition of the hydraulic cement materials to which they are added. There are occasions when the water-repellent additives are not added or in improper amounts, either in error or deliberately. Therefore, it would be important to be able to detect the presence of a properly formulated mixture during construction, and certainly before it is too late take corrective action. Furthermore, the ability to test for compliance may be a strong incentive to comply with the specified formulations.
Heretofore, water-repellent additives were not intended to be detected or quantified once the cementitious material has hardened. The evaluator is often relegated to attempt some kind of physical property measurement, such as a water uptake test or complicated and expensive analytical test. Such tests often are not very reliable for determining whether the water-repellent additive is present or for estimating whether the water-repellent additive has been added at a sufficient dosage and distribution (i.e., well-dispersed throughout the cement-based material) especially when conducted on hardened masonry mortar samples removed from a wall because of the small dimensions of the samples which are typically only ⅜ inch (10 mm) in width by 1 to 1.5 inch (25 to 40 mm) in depth.
Due to the difficulty with the prior formulations of water-repellent admixtures, organizations such as the National Concrete Masonry Association and ASTM have not recognized an analytical technique for identifying or measuring the presence of a water-repellent additive in cementitious materials, such as masonry mortar. The typical technique is to directly evaluate the level of water repellency exhibited by the cement-based material, but that is difficult due to small sample sizes that are necessary in most situations. What is desired is a method to indirectly detect and quantify the presence of the water-repellent admixture without needing to test the water repellency.
It would be beneficial to employ a tracer that can indirectly verify the presence, quantity, and/or distribution of water-repellent admixture within a cement-based material. What is needed is a tracer additive that is reliably identifiable, qualitatively and/or quantitatively, after the hydraulic cement-based material has aged and weathered over time. Desirable tracers would not oxidize and degrade over time.